Mail handling apparatuses include, for example, a weight measuring apparatus that measures the weight of mail items that are conveyed consecutively. In order to measure the weight of each mail item in a state in which it is unaffected by conveying systems on its upstream side and its downstream side, the weight measuring apparatus is built into the mail handling apparatus as a unit that is independent from the conveying systems. The mail items to be processed have different lengths in conveying direction.
In order to reliably hand over and convey the mail items to this independent unit, the distance between the weight measuring apparatus and the conveying rollers that are closest to the unit on the upstream side in conveying direction of the weight measuring apparatus (these conveying rollers are referred to in the following as “upstream-side conveying rollers”) is set to a distance that is shorter than the mail item with the shortest length in conveying direction out of the mail items that are handled by the mail handling apparatus (such a mail item is referred to in the following as “shortest mail item”). The length of the shortest mail item, as the shortest sheet, may be 14 cm in Japan, for example. The length of the shortest mail item differs for every country. Similarly, also the distance between the weight measuring apparatus and the conveying rollers that are closest to the unit on the downstream side in conveying direction of the weight measuring apparatus (these conveying rollers are referred to in the following as “downstream-side conveying rollers”) is set to be shorter than the shortest mail item.
Moreover, in order to enable the weight measurement of the mail item whose length is longest in conveying direction out of the mail items that are handled by the mail handling apparatus (such a mail item is referred to in the following as “longest mail item”), it is necessary that the distance between the upstream-side conveying rollers and the downstream-side conveying rollers is longer than at least the length in conveying direction of the longest mail item. That is to say, when measuring the weight of a mail item, it is necessary that that mail item is unaffected by the conveying systems on the upstream side and on the downstream side. The length of the longest mail item, as the longest sheet, may be 23.5 cm in Japan, for example. The length of the longest mail item differs for every country.
Thus, it is necessary that the distance between the upstream-side conveying rollers and the downstream-side conveying rollers is sufficiently long, so that the weight measurement is finished in the time after the trailing edge in conveying direction of the longest mail item that is fed into the weight measuring apparatus has left the nip of the upstream-side conveying rollers and the conveying state of that longest mail item has stabilized until the leading edge in conveying direction of that longest mail item reaches the downstream-side conveying rollers.
However, when the distance between the upstream-side conveying rollers and the downstream-side conveying rollers is made large, the length of the weight measuring apparatus in conveying direction necessarily also needs to be made large, which is problematic for example in cases where the shortest mail item is conveyed consecutively. That is to say, when the shortest mail items are conveyed consecutively with a short gap in order to achieve fast processing, a plurality of the shortest mail items will be fed simultaneously into the weight measuring apparatus, and it is not possible anymore to measure the weight of the mail items.
While it is conceivable to widen the conveying gap of the mail items, in this case the number of mail items conveyed per unit time becomes accordingly lower, and the processing capability of the mail handling apparatus drops. That is to say, in this case, high-speed processing of mail items is not possible anymore.
On the other hand, a method is conceivable in which drops in the processing capability are averted by branching the conveying path of the mail items, arranging a plurality (for example two) weight measuring apparatuses in parallel, and guiding the mail items alternatingly to these measuring apparatuses. However, in this case, the manufacturing costs of the apparatus increase, and also the installation space for the apparatuses increases.